Rebuffering is caused by fluctuations or changes in Internet connection speed. This error will occur even if Web pages load quickly or even after a good test result from a third-party speed test Web site through a computer. This is because when trying to watch a movie from Netflix, the Internet connection cannot maintain a high speed for a long period of time, so the movie has to pause and rebuffer.
Perform both speed and ping tests to check not only speed, but look for packet loss. Try testing by connecting wired to see if you are experiencing Interference. are you on a VOIP line? If you are experiencing speed issues consult your local ISP or check your network topography.